Material distributing system for mining dredges



Dec. 20, 1955 C. V. DEAVER MATERIAL DISTRIBUTING SYSTEM FOR MINING Filed Aug. 20, 1952 DREDGES 2 Sheets-Sheet 1 a INVENTOR. (#40155 K film Dec. 20, 1955 c. v. DEAVER 2,727,623

MATERIAL DISTRIBUTING SYSTEM FOR MINING DREDGES Filed Aug. 20, 1952 2 Sheets-Sheet 2 INVENTOR. [may 140mm? United States Patent 2,727,623 MATERIAL DISTRIBUTING SYSTEM FOR MINING DREDGES Charles V. Deaver, Yuba City, Calif., assignor to Yuba onsolidated Gold Fields, San Francisco, Calif., a corporation of Maine Application: August. 20, 1952, Serial No. 305,385

2 Claims. (Cl. 209-44) My invention relates to mechanism for recovering values, such as gold and platinum, from alluvial gravel deposits in which the values are found. A major way of recovering such values is first to dredge the material from its site by means of bucket dredges and to separate the gravel and rocks from the finer sands and the values by means of the customary screening or separating mechanism. The value, say gold, is then recovered from thefiner sands by amalgamation with mercury in place in sluice boxes. More recently there has been a tendency to utilize jigs for eflectuating the separation of values from the associated sand, fine earth and water. Jigs of the type referred to are shown in various patents and patent applications; for example, the patent to Macaulay, No. 2,416,450, issued February 25, 1947, and the copending patent application of Von Bolhar, Serial No. 144,156, filed February 14, 1950, now Patent No. 2,698,686.

Since in most installations the number of jigs employed is relatively large, and since the installation is not a stationary one but is on the floating hull of a dredge, there arises a problem of distributing the material to the various jigs as it is dredged up from its site. The problem is to prevent any of the jigs being substantially overloaded yet to keep all of the jigs eflective at a maximum rate and to do so despite variations in the type of material which is dredged from time to time, despite variations in position of the dredge hull from time to time, and despite differences in the rate of operation of the dredge as a whole.

It is therefore an object of my invention to provide a material distributing system for mining dredges effective to achieve the various aims indicated.

A still further object of my invention is to provide a material distributing system which has the effect of maintaining the jigs at a maximum rate of recovery or substantially so.

A still further object of my invention is to provide a material distributing system which rnay be readily installed on mining dredges already in existence and which utilizes many of the facilities already available on. such dredges.

A still further object of the invention is to provide a material distributing system which can economically and readily be installed to displace sluice boxes and riflles and provide improved and more satisfactory operation with igs.

Other objects, together with the foregoing, are attained in the embodiment of the invention described in the accompanying description and illustrated in the accompanying drawings in which Figure l is a cross section transversely through a dredge showing the general arrangement of the material distributing system of the invention, with parts of the mechanism being broken away to simplify and reduce the size of the figure and other parts being represented diagrammatically.

Figure 2 is a side elevation of a portion of the distribution system, part of the structure being broken away, and

ice

2 part being shown in cross section the plane of which is indicated by the line 2-2 of Figure 1.

Figure 3 is a plan of a portion of a dredge showing the distribution system and associated structures, some parts being broken away.

While my material distributing system can be embodied in a large number of different ways, depending on the particular mining dredge on which it is to be installed and depending. also on the surrounding dredging conditions, it has satisfactorily been embodied and installed on several dredges in accordance with the arrangement illushated and described herein.

The mechanism is located on a dredge hull having a deck for receiving the machinery. Material excavated from its natural site in the dredge pond onwhich the hull floats is recovered in the usual way by a bucket line, not illustrated. The dug material is discharged by the bucket line into the interior of a circular-cylindrical, revolving, perforated grizzly or trommel 8. The trommel 8 is arranged with its longitudinal axis 9 inclined downwardly and is normally disposed substantially along the longitudinal center of the dredge with the higher end of the trommel forward.

Material discharged by the individual buckets of the bucket line and including rocks, gravel, sand, finer earth and the values to be recovered is discharged into the interior of the trommel and travels by gravity downwardly along the length of the screen Walls as the trommel is revolved by power. Powerful jets 10 of water spray against the material as it traverses the interior of the trommel particularly along the bottom thereof. The coarser parts such as boulders, large rocks and the like pass entirely through the trommel and are discharged by a tailings stacker, not shown, in the customary way.

The finer particles pass through perforations 6 in the trommel 8 and are received in a screen casing 11 having sides 12 leading downwardly to a central discharge slot 13 or opening. In the preferred arrangement, the material is divided into two similar parts for treatment by substantially identical installations symmetrically disposed on opposite sides of the center of the dredge. Since the installation on one side of the dredge is substantially a duplicate of that on the other side, the description of one installation applies equally to the other.

For diverting the material passing through the slot 13 substantially equally to the opposite sides of the dredge, the casing 11 is provided with distributing channels 16 and 17 alternating in direction so that similar portions of the material pass alternately to each side as the material traverses the slot 13 longitudinally. A. representative supply of material, including the coarser gravel, and sand and the fine earth and the values falls into a box or settling chamber 18 on one side of the dredge, along with a large quantity of Water which has been discharged onto the material inside the screen trommel 8.

Since the screen is inclined, the settling chamber 18 is only one of many arranged in vertical steps longitudinally of the dredge hull. All of the settling chambers are alike, and the description of one applies to the others. Because of the inclination of the screen 8 and because the deck 7 of the dredge hull moves from time to time due to the difference in trim of the floating dredge, the settling chambers 18 are spaced close to each other and are set along the length of the trommel so that each one of them is as nearly as possible level. They provide a number of stepped, substantially level sections almost entirely separate from each other.

Material which falls through the discharge slot 13 into one of the settling chambers 18 is quite fluid, copious amounts of washing water being present. In the chamber 18, some gravitational separation is immediately experienced so that the heavier particles of sand, earth and values 3 tend to fall toward the bottom 19 of the settling chamber whereas the remaining somewhat clarified water and some fines flow over a level weir 21. The overflow is relatively large in quantity.

The material flowing over the weir 21 falls into overflow launders 22 stepped along the various individual settling chambers 18 and receiving the overflow from each pair of them. Some settling may take place in the launder so that the top portion of the flow is largely water with only a small amount oi? values in it. This top portion of fluid from each launder 22 is received in one of a series of troughs 23 leading to further processing equipment. This includes a settling device 24 of substantial dimensions wherein the material is relatively quiescent for separation by gravity. The overflow from the settling tank 24 is almost entirely devoid of values and is discharged as water into a suitable flume 26 leading overboard into the dredge pond. The heavier material, including the values, settles toward a bottom outlet 27 in the separator 24 from which it travels through a conduit 28 to a recovery mechanism.

The conduit 28 leads to a sump tank 29 at the inlet of a pump 31. Another settling tank 32 at a higher location on the dredge receives the pump discharge through a conduit 33 and serves for further separation of the heavy material by gravity. The light liquid and fines of substantially no value flow overboard from a tank outlet 34 while the heavy materials, including the values, flow through a bottom discharge line 36 to recovery mechanism, such as jigs 37. Here, again, the overflow is discharged through a top line 38 while the values are recovered from bottom openings 39.

The settling chamber 18 in addition to the weir 21 also has a number of relatively restricted discharge openings 41 in the bottom thereof. Sand, heavy particles, and values fall by gravity through the openings 41. The density of the mixture in the settling chamber 18 is considerably greater toward the bottom of the chamber than it is toward the top. It is especially desired to equalize the nature of the material in the various settling chambers because the discharge from the trommel or grizzly varies along its length. There is consequently provided a transfer aperture 42 or side wall opening in each settling chamber leading into the next adjacent lower settling chamber. Although the material discharging from the grizzly into the casing 11 is by no means uniform in quantity or composition throughout the length of the grizzly, it is possible, by regulating the size and height of the apertures 42, to elfectuate a general lengthwise distribution of the material from the higher settling chambers toward the lower ones so that the material released through the discharge opening 41 from each of the settling chambers is then more nearly uniform.

The material falling through the openings 41 enters a boil box 4-3 wherein it is thoroughly mixed by turbulence. The mixed material then flows over an apron or duct 44 onto the upstream one of a pair of jigs 4'6 and 47 arranged in series transversely of the dredge hull. The jig pairs are disposed side by side for approximately the length of the trommel. Each jig 46 receives material from the adjacent settling chamber 18, each settling chamber having an appropriate jig installation. The sand, gravel,

values and water from the apron 44 pass toward the left in Figure 1 over the bed of the first jig 46. The values and heavy mixed material fall to the bottom of the jig hutch and flow out through a duct 48 from which they travel with other materials in the conduit 28 for subsequent separation. The supernatant material passing from the jig 46 travels to the second jig 47 of the pair where it is similarly handled, the heavy discharge going through a duct 49 to be carried with other fluid in the conduit 28. The fluid discharged from the jig 47 flows into the flume 26 since it is almost entirely aqueous and has substantially no values in it and so is returned to the dredge pond.

With this arrangement, the discharge from the grizzly or trommel is appropriately distributed and handled, with the large amount of Water needed for washing being diverted or removed early in the process although without loss of values. The remaining material is consequently processed in a less bulky or voluminous way without overloading the jigs either with Water or with surges of solid material.

What is claimed is:

1. A material distributing system for mining dredges comprising a longitudinally extending screen adapted to discharge material along its length, a plurality of stepped settling chambers arranged along said length for receiving said material, each of said chambers having an overflow weir and a bottom discharge opening, a plurality of first jigs, a plurality of ducts, each duct being arranged to conduct material passing through one of said discharge openings over one of said first jigs, an overflow launder disposed to receive material discharged from a plurality of said weirs, a second jig, and means for conducting material received from said overflow launder over said second jig.

2. A material distributing system for mining dredges comprising a longitudinally extending screen downwardly inclined in the direction of its length and adapted to discharge material along its length, a plurality of settling chambers arranged in steps of different height below said screen for receiving said material, each of said chambers having an overflow weir and a bottom discharge opening, means for establishing communication between said settling chambers from the highest toward the lowest, a plurality of jigs at least one being arranged below each of said settling chambers, a plurality of ducts, each duct being arranged to conduct material from the bottom discharge opening of one of said settling chambers to flow over an associated one of said jigs, an additional jig, and means for conducting material from said overflow weirs to said additional jig.

References Cited in the file of this patent UNITED STATES PATENTS 509,818 Lockhart Nov. 28, 1893 594,829 Hallett Nov. 30, 1897 652,900 Postlethwaite July 3, 1900 1,231,297 Rober June 26, 1917 1,272,301 Nelson July 9, 1918 1,719,442 Newsom July 2, 1929 2,487,845 Bird Nov. 15, 1949 

